ISOLATION AND CHARACTERIZATION OF A MOLYBDENUM-REDUCING AND GLYPHOSATE-DEGRADING Klebsiella oxytoca STRAIN SAW-5 IN SOILS FROM SARAWAK

Abstract: Bioremediation of
pollutants including heavy metals and xenobiotics is an economic and
environmentally friendly process. A novel molyb-denum-reducing bacterium with
the ability to utilize the pesticide glyphosate as a carbon source is reported.
The characterization works were carried out utilizing bacterial resting cells
in a microplate format. The bacterium reduces molybdate to Mo-blue optimally
between pH 6.3 and 6.8 and at 34oC. Glucose was the best elec-tron donor for
supporting molybdate reduction followed by lactose, maltose, melibiose,
raffinose, d-mannitol, d-xylose, l-rhamnose, l-arabinose, dulcitol,
myo-inositol and glycerol in descending order. Other requirements include a
phosphate concentration at 5.0 mM and a molybdate concentration between 20 and
30 mM. The molybdenum blue exhibited an absorption spec-trum resembling a
reduced phospho-molybdate. Molybdenum reduction was inhibited by mercury,
silver, cadmium and copper at 2 ppm by 45.5, 26.0, 18.5 and 16.3%,
respectively. Biochemical analysis identified the bacterium as Klebsiella
oxytoca strain Saw-5. To conclude, the capacity of this bacterium to reduce
molybdenum into a less toxic form and to grow on glyphosate is novel and makes
the bacterium an important instrument for bioremediation of these pollutants.